1. Field of the Invention
The present invention relates to a processing apparatus for hot-air treatment of a fiber constituting a nonwoven fabric to produce the nonwoven fabric and a processing process for the same. More specifically, the invention relates to a processing apparatus and a processing method for producing a point-through-air nonwoven fabric wherein hot air is allowed to penetrate through spots of a web or a sheet-like article and fibers at the penetration sites are thermally bonded.
2. Description of the Related Art
As methods for bonding between fibers for nonwoven fabric production, a thermal bonding method, a chemical bonding method, a needle punching method, a water-stream entangling method and the like are generally known. As processing methods for the general thermal bonding method, a hot-air through-air processing method and a hot-roll press-fixing processing method are known.
The hot-air through-air processing method is a method wherein a heat-bondable conjugate fiber comprising a low-melting component and a high-melting component is used as a web and hot air at a temperature of the low melting point or higher and the high melting point or lower is allowed to penetrate. A nonwoven fabric obtained by this method has both of bulkiness and strength but has a drawback in that flexibility is impaired since fiber-entangling points are wholly heat-bonded.
The hot-roll press-fixing processing method is a method wherein press-processing is performed with a pair of two hot rolls. A nonwoven fabric obtained by this method has high strength but there is a drawback in that bulkiness and flexibility are impaired. As a method which overcomes the drawback, a point-bonding heat-press-fixing processing method is exemplified. However, even by this method, it is difficult to obtain sufficient bulkiness.
Accordingly, in order to provide bulkiness and flexibility to a nonwoven fabric together with sufficient strength, there has been used a point-through-air processing method wherein regions through which hot air is allowed to penetrate and regions with which hot air is not brought into contact are mixed on a heat-bondable conjugate fiber web and the web is processed. As described in Japanese Patent No. 4206570, the processing method of a point-through-air nonwoven fabric is a processing method utilizing a hot-air processing machine (suction band dryer). Specific examples include a method comprising placing a heat-bondable conjugate fiber web on a conveyer net of the hot-air processing machine, inserting a spacer so as not to crush the bulkiness of the web as far as possible, sandwiching it between punching boards, and treating it with hot air at a low velocity; a method comprising changing the conveyer of the hot-air processing machine to a porous one, placing a fiber web thereon, and treating the web with hot air; and a method comprising using a hot-air processing machine having porous conveyers above and below, sandwiching a web, and treating it with hot air.
In the case where a nonwoven fabric is formed by such a point-through-air processing method, since hot air is passed through the punching board to penetrate through the heat-bondable conjugate fiber web, the heat-bonded parts where fibers are bonded by heat is interspersed in the nonwoven fabric. Since the heat-bondable conjugate fibers are bonded to one another in the heat-bonded part regions, strength can be provided to the nonwoven fabric. On the other hand, bulkiness and flexibility can be provided by non-heat-bonded part regions to which hot air was not applied.